87 Vanagan Camper Power Window Problem

The passenger side power window won't go down more that 2-3 inches. It
doesn't seem to be the switch as it's the same using with the drivers or
passengers switches (actually it's a button for up and down). In addition,
I have taken off the inside cover of the door and greased the guide or
slide so that the window goes up and down manualy but the electric motor
still won't pull it up or down more that a couple of inches.

So my question is:

Is this a problem with the electric motor that drives the window up and
down?

Are there any diagrams on the net of this? Bentley doesn't do a very
good job of diagraming this. Actually there is a plastic piece that directs
the cable around a curve that is loose in there that I need to put into
place as well.

And are the power window motors for this model interchangeable with other VW
products that I might find in the boneyard? e.g Jetta or Golf. or are these
electric motors repairable?

Any other solutions?

Thanks in advance for any assistance

Wray